Chemical Water Treatment Methods

Beware water treatment chemicals are dangerous, safety first! Use them in a well-ventilated area and wear appropriate PPE such as eye protection. Instructions vary. Do your research and store instructions with treatment methods.

Why Chemical Disinfection?

The major public health organizations all preach that boiling water is the “preferred” emergency water treatment method. Admittedly, chemical water treatment methods do you have some drawbacks:

Some water treatment chemicals have limited shelf lives. This varies greatly depending on the form of chemical and method of storage.

Instructions differ from chemical to chemical which makes them difficult to remember. Concentration and contact time also vary with turbidity (cloudiness) and temperature.

Some chemicals are less effective against parasites.

Effectiveness can vary with pH.

Water treatment chemicals are dangerous if used improperly.

Some chemicals are not accompanied by adequate instructions even when packaged and marketed for water treatment.

The upsides of chemical water treatment are too great to overlook:

Chemicals are lightweight compared to filters. This makes them ideal for inclusion in Personal Survival/Self-Recovery Kits.

Some water treatment chemicals are multi-use.

Firing up a heat source to boil water may not be practical, possible, or safe in an emergency.

If the power is out, boiling water uses valuable fuel that may be difficult to replace during or immediately following an emergency.

Steps Common to Chemical Water Treatment Methods

Regardless of the chemical used, follow the directions that come with the product. Treated water must be stored in a clean container. Contaminated containers must be cleaned with treated water before use. They must also be disinfected before treated water is stored in them.

Here are some general guidelines. After the chemical is added to the water, wait at least 5 minutes for it to completely dissolve unless it is effervescent. Shake or mix well. Then disinfect any canteen thread, caps, taps, closures valves, etc. Loosen caps or closures just enough for water to pass. Hold the caps or closures in place while briefly inverting or shaking the vessel to wet them. Make sure all surfaces that may come in contact with the water are coated with the treatment solution. If the vessel has taps, like a lister bag, make sure you flush them. Otherwise the treated water may be re-contaminated by pathogens on untreated surfaces.

Some product instructions are overly simple and don’t take turbidity or temperature into account. A rule of thumb is to double exposure time for water that is cold (5°C/41°F or lower), double the chemical dose for water that is turbid, and do both for water that is both cold and turbid. The water may taste bad, but at least it will be safe. If you are in a hurry, doubling dosage cuts exposure time in half at the cost of taste.

If strong chemical taste is an obstacle to hydrating, use powdered drink mix to mask the taste. Don’t add anything until after exposure time is completed. Adding drink mix before this point will diminish effectiveness.

Chlorine-Based Chemical Water Treatment Methods

Chlorine-based chemicals are widely used in water treatment plants and have been in use for more than two centuries. Use chlorine-based treatments immediately once opened. Instructions for most products may list shorter exposure times, but four hours of exposure time is recommended. This additional time is for maximum efficacy against Cryptosporidium. Chlorine concentration varies from 2-4 ppm for clear water and 4-8 ppm for turbid water, depending on the public health organization making the recommendation. Filtering water before chlorine treatment lowers the amount needed, shifting it towards the lower end of that range. Free chlorine drops substantially within 30 minutes, which is another reason to let water sit after exposure. The CDC considers residual concentrations up to 4ppm safe to drink.

Chlorine-based water treatment products typically affect taste and odor more severely than iodine-based products. However, the ability to taste and smell chlorine varies from person to person. After adequate exposure time, water treated with chlorine-based products can be aerated to improve taste and odor. Pour the water back and forth between two clean containers several times, then let it stand for several hours. The effectiveness of chlorine-based products are significantly diminished by biomatter and other debris.

One benefit of chlorine is that it can often be used by people who are iodine intolerant. Chlorine is more effective against giardia and Cryptosporidium than iodine. Although insufficient concentration or contact time, aged disinfectant, turbidity (cloudy water), cold or high pH can prevent effective disinfection depending on the product used.

Common Chlorine-Based Water Treatment Products

Chlorine-based products may come as liquid, tablets, effervescent tablets, or powder sachets. Some of the more common products are:

Troclosene Sodium or Sodium Dichloroisocyanurate (NaDCC) Tablets

Potable Aqua®

Aqua Mira®

Reset®

Pyramid Biox®

Quip Laboratories®

LY-Tab®

LY-Powder®

Katadyn Micropur®

Oasis®

Chlorine Dioxide

Chlorine dioxide has different properties than other chlorine disinfection products and is effective at lower ppm. Don’t store opened tablets or powder or re-pack as ClO2 reacts with air. More effective than chlorine against oocysts, Legionella, and at higher pH (above 7). If need is not urgent, waiting 4 hours will ensure maximum efficacy.

Chlorine Bleach Solution – 5-6%

Chlorine bleach is multi-use and important to have on hand for hygiene. Dose 2 drops per liter for filtered water or 3 drops per quart or liter of tap water at 15°C/60°F. Shake or stir. Let stand for a minimum of 30 minutes. Double exposure time if water is cold (5°C/41°F or lower), double number of drops for turbid water. Household bleach should only be used for water treatment in emergencies. Use only regular, unscented household bleach. Don’t use scented bleach, color-safe bleach, gel (no splash), or bleach with added cleaners. Chlorine bleach diminishes in strength by approximately 20% when stored for a year between 50° & 70°F, and diminishes approximately 20% per year thereafter.

Treated water should have a slight chlorine odor. If treated water lacks a slight chlorine odor, treat again and let stand for an additional 15 minutes before use. Pour treated water back and forth from one clean container to another (aerate) several times. Let stand for several hours to diminish chlorine smell and taste before consumption.

8.25% Sodium Hypochlorite Chlorine Bleach Solution

Same as above, but use 2 drops per quart or liter.

1% Bleach or Bleach of Unknown Chlorine Concentration

Only use in an emergency and when bleach is not available or has lost potency. Pool shock must be high-test calcium hypochlorite (HTH) with a free chlorine content of 60-70%. Mix in a well-ventilated area and wear eye protection. This is potent stuff. An MRE spoon of this will treat 100 gallons of water.

To treat small quantities, make a bleach solution and use that to treat water as you would use bleach. Add 1/4 ounce (7.9ml or approximately one heaping teaspoon if you have measuring spoons) to 2 gallons of water and stir until particles dissolve to create 8% bleach solution. Don’t try to cut this formula to treat 1 liter because the amount of HTH would be less than 1 ml in volume and is too small to measure reliably. Verify free chlorine content of water with free chlorine test strips. If HTH figures into your backup emergency plans, be sure to store test strips as they very well may keep you from burning up your kidneys. Free chlorine should be approximately 10ppm to treat clear water and 20ppm to treat turbid water. Properly stored, HTH will not begin diminishing in strength for up to 10 years.

Sodium Troclosene or Sodium Dichloroisocyanurate (NaDCC)

Typically come in effervescent tablet form. NaDCC solution can also be used for disinfection of infected wounds, instruments, equipment, linen, floors, and surfaces. Tablets are tiny so they fit in the smallest mini survival kits and pocket kits.

Iodine Based Water Treatments

Iodine shouldn’t be used by people who are iodine intolerant, pregnant, have diseases of the thyroid, or hyperthyroidism. Iodine should not be exposed to sunlight. To get rid of the nasty taste iodine methods impart to water, crush a tablet of vitamin C and add a little (approximate 50 mg) to treated water after exposure time has elapsed. If you add it too soon, the disinfection process will be stopped in its tracks. Powdered drink mixes containing vitamin C have the same effect.

Common Iodine Products Used for Water Treatment:

Potable Aqua®

Globaline®

EDWGT®

Povidone-Iodine Solution/ Betadine® Solution

Tetraglycine Hydroperiodide Tablets

Iodine Tincture 2%

Iodine Topical Solution 2%

Lugol’s Solution® 5%

Iodine Crystals (Polar Pure®)

Povidone Iodine Solution 10% Prep Pads

I have seen some bad information being passed around about this. Some survival kit manufacturers will toss a PVP prep pad in and call it a water treatment method. They give instructions to add half a pad to a quart of water. The problem is that the amount of iodine in pads varies wildly (from .67ml to 10ml) when new and dries out over time.

If you have to use a prep pad, wring it out into the water, counting the drops. If it didn’t have enough drops, look at the pad and judge how many drops of PVP Iodine are still in the pad as best you can. It will be very few, so add the pad or a portion thereof to introduce the number of drops indicated.

2% Tincture of Iodine or 2% Iodine Topical Solution

Povidone Iodine 10% Solution/Betadine® Solution

4 drops per quart, other than that, same as 2% tincture or topical solution. Povidone iodine is preferable to tincture of iodine or Lugol’s Solution® for austere medicine. This is due to greater stability and longer lasting anti-septic effect.

Lugol’s Solution® 5%

Alcohol-free aqueous solution. 4 drops per quart, other than that, same as 2% tincture or topical solution.

Iodine Crystals (Polar Pure®)

Follow instructions on bottle. Fill bottle with water and shake, then wait 1 hour. Add number of capfuls indicated on bottle then swirl. Wait 30 minutes for warm water, 60 minutes for cold. 15ml solution for clear water, 30ml for cloudy.

Probably the most commonly available iodine tablets. Follow instructions on box.

Potassium Permanganate

Probably the most multi-use chemical you can put in pocket survival kit, but handle with extreme caution. Mix it too strong and it becomes caustic. It will also cause fingernails to scale so keep your fingers out of the solution. Also known as Condy’s crystals, permanganate of potash, and chameleon mineral, potassium permanganate is a strong oxidizer. Must be stored in a non-reactive container. Removes manganese, iron, sulfides, many odors, controls nuisance biological growth, and improves taste of water in wells, cisterns, ponds, and tanks.

Potassium Permanganate Crystals or Tablets

If tablets, then crush and use as crystals. Add 2-4 tiny (<1mm) crystals per liter until water turns a light pink color. Wait 30 minutes.

Add crystals until darker pink for wound irrigation. Remove 1mm from the corner of an MRE hot beverage bag or plastic bag and squeeze gently to develop pressure for irrigation. Add crystals until red for canker sores & anti-fungal treatment. Add until deep red or purple for signaling on snow. Add a little glycerin and a violent exothermic reaction will occur that can start a fire if needed.

Final Thoughts

Even though chemical water treatment can affect the way your water taste and smells, it is highly effective at making it safe. Just make sure you store and handle it properly. Be very careful to follow instructions as it can be dangerous otherwise.